Tobacco smoke filter

ABSTRACT

A filter for removing harmful ingredients from tobacco smoke without unduly increasing the draw including at least one section of a rod composed of longitudinally extending and generally parallel continuous cellulose acetate fibers and at least one very thin disc composed of randomly deposited wood cellulose fibers abutting a rod section, the rod section and disc being closely confined within an impervious shell. Preferably, a plurality of discs are sandwiched between two of the rod sections. The discs composed of wood cellulose fibers occupy only a very small fraction of the total length of the filter.

United States Patent 1191 Southwest Building, Houston, Tex. 77002; Benjamin H. Thurman, Rt. 4, Culpeper, Va; 22701 6 Clayton et a]. May.7, 1974 [54] TOBACCO SMOKE FILTER 2,847,086 8/1958 M11116: 131/261 R x [76] Inventors: Benjamin Clayton, 1621 Bank of the Primary Examiner-Melvin D. Rein Attorney, Agent, or Firm-Bacon & Thomas [57] ABSTRACT A filter for removing harmful ingredients from tobacco smoke without unduly increasing the draw ineluding at least one section of a rod composed of longitudinally extending and generally parallel continuous cellulose acetate fibers and at least one very thin disc composed of randomly deposited wood cellulose fibers abutting a rod section, the :rod section and disc being closely confined within an impervious shell. Preferably, a plurality of discs are sandwiched between two of the rod sections. The discs composed of wood cellulose fibers occupy only a very small fraction of the total length of the filter.

1 Claim, 3 Drawing Figures TOBACCO SMOKE FILTER The present invention relates to a tobacco smoke filter and more particularly, to such a filter which will efficiently remove harmful ingredients, commonly referred to as nicotine and tars, from the smoke without increasing the draw to an objectionably high level.

The principal use contemplated for the present filter is in conjunction with a cigarette, but it is to be understood that it is of general application and can be employed with any type of smoking article, e.g., a pipe, cigar or cigarette or cigar holder.

Many types of filters have been proposed fordecreas ing the amount of the harmful ingredients of tobacco smoke reaching the smoker, but many of them are found wanting because of the fact that to be truly satisfactory, a filter must not only remove a high proportion of the harmful ingredients but must do this without unduly impeding the passage of the smoke so as to result in too high a draw. Another factor of primary importance is, of course, that the filter must be capable of inexpensive fabrication so as not to make too costly the smoking article with which it is used.

The so-called cellulose acetate filter rod, which comprises a mass of generally parallel cellulose acetate filaments, admirably meets the requirements of good draw and economy, and the major proportion of the filter cigarettes now on the market embody thisfilter. However, by itself, this type of filter does not remove as much of the nicotine and tars as is desired. In this regard, the construction of the filter rod is such that the smoke is not always evenly distributed in its passage therethrough and becomes channeled, thus considerably lessening the efficiency of the filter.j

Accordingly, it is an object of the invention to provide a filter for tobacco smoke which will remove a high proportion of the nicotine and tars contained therein.

Another object of the invention is to provide a filter for tobacco smoke which will not unduly increase the draw.

yet another object of the invention is to provide a filter for tobacco smoke which causes the smoke to be evenly distributed when passing through it without channeling.

Still anotherobject of the invention is to provide a filter for tobacco smoke which does not destroy the taste of the tobacco.

A further object of the invention isto provide a highly efficient filter for tobacco smoke which is economically produced.

A more specific object of the invention is to provide a cigarette incorporating a filter which has all of the attributes detailed in the foregoing objects.

Other and further objects of the invention will be apparent from the following detailed description taken in conjunction with the drawings in which:

FIG. 1 is a longitudinal section illustrating a cigarette incorporating a filter which is a preferred embodiment of the invention;

FIG. 2 is a cross-section taken on the line 2-2 of FIG. 1; and

FIG. 3 is a cross-section taken on the line 33 of FIG. 1.

It has unexpectedly been found that the ability of the. conventional cellulose acetate filter to remove nicotine and tars can be greatly enhanced by associating therewith at least one and preferably a plurality of very thin discs of high porosity composed of randomly deposited and intertangled wood cellulose fibers, and that this can be done while still maintaining a satisfactory draw. The conventional cellulose acetatefilter rod comprises a continuous filamentary tow of plasticized cellulose acetate fibers. The term continuous filamentary tow is intended to define a material such as that which results when filaments extruded from a plurality of spinnerets are brought together and combined to form a continuous body of fibers randomly oriented primarily in a longitudinal direction. In such a tow, the filaments are generally longitudinally aligned in substantially parallel orientation, but include crimped portions which may form short sections running more or less at random in non-parallel diverging and converging directrons.

Generally, the fibers of the tow emerging from the spinneret are bunched together to form a raw tow which is collected into a bale for subsequent process ing. Such processing usually involves, in addition to unwinding of the.raw tow, spreading apart of the fibers to provide a relatively thin layer of the same, tensioning of the fibers to render the crimp of uniform character, impregnating the fibrous layer with a plasticizer to bind adjacent fibers together, and gathering the bonded layer through a suitable funnel or the like to form a treated cylindrical tow which is overwrapped in a suit able paper to produce a stable elongated element. This overwrapped rod is then generally severed into segments which are cured and later cut into substantially equal size filter plugs. The curing" procedure has ordinarily been commercially effected by either heating the paper-covered segments in an oven to allow the palsticizer to permanently bond the tow fibers together,.or merely by permitting the segments to age for an extended period of time in an unheated condition.

Such a filter rod is fully described by U. S. Pat. No. 2,900,988 which issued on Aug. 25, 1959.

The sheets of matted wood cellulose fibers from which the discs are formed may conveniently comprise ordinary toilet tissue, which as is well known is highly absorbent and permeableto air. Such sheets are very thin rangingfrom about 0.002 to about 0.004 inches, usually about 0.003 inches, in thickness.

The air permeability or porosity of individual sheets of toilet tissue can vary considerably. For example,

tests were carried out in accordance with ASTM test method D 737-69 on three commercially available threads of toilet tissue, Rocky Mountain, manufactured by the Ford Howard Paper Co. of Green Bay, Wisconsin, and Zodiac and Scott Tissue, both manufactured by the Scott Paper Co., Philadelphia Pa., and the average air permeabilities were to be respectively, 54, 93 and 108 cubic feet/minjft All of these tissues are suitable for the production of discs for use in filter assemblies of the present invention.

The length of cellulose acetate rod included in the filter assembly of the invention may vary depending on the amount of tars and nicotine to be removed from the tobacco smoke and the resistance to draw effected by the thin disc elements. Ordinarily, the length of filter rod present can correspond to that used in commercially available cigarettes employing this type of filter, namely, from 15 mm. to 25 mm. A total length of cellulose acetate filter rod of about 20 mm. has been found to give uniformly good results.

The discs of wood cellulose fiber are punched out of a sheet so as to have the same diameter as the cellulose acetate filter rod, and in a preferred embodiment of the invention a plurality of discs is sandwiched between two sections of filter rod with the discs in alignment and closely packed between the rod sections with the outermost discs abutting opposed ends of the filter rods. It is also preferred that the rod sections be of unequal length with the shorter section being the one nearest the source of tobacco smoke. For instance, a plurality of thin cellulose wood fiber discs may be sandwiched between cellulose acetate rod sections of mm and 5 mm in length.

The number of wood cellulose discs may vary considerably in accordance with their individual porosity and the amount of tars and nicotine to be removed from the tobacco smoke being filtered. Even a single disc has been found to cause removal of undesirable ingredients to a much greater extent than can be accounted for by the total length of cellulose acetate filter rod which is present. As many as seven cellulose fiber discs have been successfully employed, but generally the optimum number of discs will range between three and five. In all instances, however, the discs will occupy only a very small fraction of the total length of the filter assembly of the invention.

When a plurality of wood cellulose fiber discs are employed, they may be produced simultaneously by a single punching from stacked sheets of tissue. It has been found that a plurality of discs are so produced remain loosely adherent so that they can be handled easily as a unit for incorporation into the filter construction according to the invention.

While there has been described a preferred embodiment of the invention wherein the wood cellulose discs are sandwiched between sections of cellulose acetate filter rods, it is to be understood that the discs may be positioned so as to abut the end of a single filter rod facing the source of the tobacco smoke to be filtered. In a cigarette, the discs may be positioned between the end of the filter rod and the cylinder of tobacco so as to be maintained in place. If used in a smoking article where such an element is not available, resort may be had to another type of support, such as a ring of stiff material. In all instances, however, there must be avoided a construction including any element which will obstruct the passage of tobacco smoke to any degree substantially greater than is caused by the combined effect of the cellulose acetate rod, wood cellulose fiber discs and the.tobacco, itself.

The filter assembly of the invention will be maintained as a unit by encasing it in the usual manner in a shell or overwrap. In the case of a cigarette, there may be employed, as is also conventional, a tipping overwrap which extends beyond the filter assembly and secures it to the tobacco-filled section.

As stated earilier, wood cellulose fibers and sheet material formed therefrom are known to be highly absorbent. However, taking into consideration the extremely small proportion of the volume of the filter as a whole represented by the wood cellulose fiber discs, it is clear that the amount of tar and nicotine removed cannot be explained by this factor, alone. Without wishing to be bound thereby, it is theorized that the porous discs act as a diffuser to effect an even distribution of the smoke which minimizes to a great degree the tendency for it to become channelized as it passes through the major length of cellulose acetate rod.

A preferred embodiment of the invention is illustrated by the drawings wherein there is shown a cigarette incorporating a filter section in which a plurality of abutting thin discs composed of wood cellulose fibers is sandwiched between two filter rods composed of cellulose acetate filaments. As shown by FIG. 1, the cigarette generally designated by the numeral 1 comprises a tobacco-filled section 2 of conventional construction and a filter section 3. The filter section 3 is completely enclosed by a tipping overwrap 4 of relatively stiff material, such as the usual paper or cork sheet, the overwrap extending somewhat beyond the filter section and firmly engaging the tobacco-filled section to maintain the two sections in assembled relation.

The filter section 3 is constructed of a first and shorter length 5 of cellulose acetate filter rod and a second and longer length of cellulose acetate filter rod 6. A plurality of abutting very thin wood cellulose fiber discs 7 are sandwiched between the lengths 5 and 6 of the cellulose acetate rods, the discs and rods being of equal diameter and the outermost discs abutting the opposed ends of the filter rods.

As stated above and shown in FIGS. 1 and 2, the cellulose acetate filaments of rods 5 and 6 are continuous in nature and extend longitudinally of the cigarette in generally parallel relation, whereas, as is best shown in FIG. 3, the wood cellulose fibers of the discs 7 are much shorter in length and intertangled, lying generally in the same plane. The fibers of the disc 7 extend generally transversely to the axis of the cigarette and the assembled discs occupy only a very small fraction of the total length of the filter section 3.

Tests were conducted to evaluate the efficiency'of tobacco smoke filters according to the invention. These tests were conducted by inserting a non-filter Camel cigarette in one end of a plastic tube having an internal diameter equal to the external diameter of the cigarette. Various combinations of cellulose acetate rod and wood cellulose fiber discs in accordance with the invention were placed by hand in the plastic tube ahead of the cigarette and smoked in a cigarette smoking machine of the type described by Bradford et al. Ind. and Eng. Chem. 28, 836839 (1936).

In accordance with the report of Oct. 2 l 1970 of the laboratory of the Federal Trade Commission, a nonfilter Camel cigarette has a tar content of 26 mg./cig. and a nicotine content of 1.45 mg./cig. The draw resistance and the tar and nicotine contents of various specimens prepared as described above were determined, and it was found that tar and nicotine removal was effected in a specimen constituting a preferred embodiment of the invention to obtain figuresas low as 2.6 mg./cig. tar and 0.27 mg./cig. nicotine. As recorded in the same Federal Trade Commission report mentioned above, a Camel king size filter cigarette has 20 mg./cig. tar and 1.3 mg./cig. nicotine. The draw compared favorably to that of filter cigarettes obtainable on the open market.

Cigarettes incorporating the filter construction of the invention were smoked in a normal manner and the taste of the smoke was found to be good.

Having described our invention, we claim:

1. A filter cigarette, comprising a tobacco-filled portion and a filter portion having a smoke inlet end and randomly deposited and intertangled to form highly absorbent tissue paper with each disc having an air permeability of from 54 to 108 cuft/min/ft, said disk means having a total thickness of 0.002 inches to 0.028 inches, each disk of said disc means having a diameter substantially equal to that of said filter rods, and a tip ping overwrap encasing said filter portion and extending therebeyond to engage said tobacco-filled portion. 

1. A filter cigarette, comprising a tobacco-filled portion and a filter portion having a smoke inlet end and a smoke outlet end, said filter portion comprising first and second sections of relatively great combined length, said sections being filter rods composed of generally parallel cellulose acetate fibers, one of said sections being positioned at the smoke inlet end of the filter portion and the other at the smoke outlet end, and porous disc means sandwiched between said sections of filter rod, said disc means consisting of from one to seven discs composed of matted wood cellulose fibers randomly deposited and intertangled to form highly absorbent tissue paper with each disc having an air permeability of from 54 to 108 cu.ft/min/ft2, said disk means having a total thickness of 0.002 inches to 0.028 inches, each disk of said disc means having a diameter substantially equal to that of said filter rods, and a tipping overwrap encasing said filter portion and extending therebeyond to engage said tobaccofilled portion. 